As a background art of this technical field, there have been known remote copy that manifolds data to hold it among a plurality of storage apparatuses located at a plurality of sites in case of a disaster such as an earthquake or a fire, and operation of storage apparatuses utilizing this feature (for example, refer to PTL1, US 2005/0033827 A)
The remote copy is categorized into synchronous remote copy and asynchronous remote copy. In the synchronous remote copy, a storage apparatus transfers data to a copy destination storage apparatus in synchronous with a write command from a host computer. In the asynchronous remote copy, a storage apparatus transfers data to a copy destination storage apparatus after responding to a write command from a host computer. The aforementioned US 2005/0033827 A is categorized as the latter.
To use either one of the remote copy functions, different host computers connect to storage apparatuses placed at separate sites (primary site and secondary site), as described in the aforementioned US 2005/0033827 A. Upon occurrence of a disaster at the primary site, operations of both of the host computers and the storage apparatuses are switched to the secondary site. This operation minimizes data loss and suspension of operations even if a site suffers from a disaster.
In the meanwhile, not against a disaster that affects the overall site as described above but against a failure in a host computer at a site, there is a known technique to protect data and prevent suspension of operations. This technique is called clustering, in which a plurality of host computers share the same volume in the same storage apparatus. If one of a plurality (assuming N+1) of host computers develops a failure, one of the remaining 1 to N host computers takes over the operations performed by the failed host computer to minimize the suspension of operations.
The reason why the host computers share the same volume in the same storage apparatus is, when a failure occurs to a host computer, to allow another host computer which takes over the operations to use data generated or altered by the host computer before the failure occurs.
In typical, a storage apparatus in such a system employs a redundant array of independent disks (RAID) configuration within the apparatus to protect data, independently from the host computers. Also, because of increase in data volume, an environment including a plurality of storage apparatuses at a site has been common in recent years. A larger scale of storage system requires more complex management; accordingly, it is expected that storage systems implementing storage virtualization as disclosed in PTL 2, US 2008/0034005 A will prevail.